The present application is based on and claims priority from Japanese Patent Applications Hei 10-143008 filed on May 25, 1998 and Hei 10-200553 filed on Jul. 15, 1998, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a stator of a vehicle ac generator driven by an internal combustion engine and a method of manufacturing the same.
2. Description of the Related Art
It is known that a plurality of conductor segments are welded to form a stator winding of a stator of an ac generator for a vehicle. For example, WO92/06527 discloses a stator whose stator winding is formed of a plurality of U-shaped conductor segments. The conductor segments are inserted from an end of the stator core and connected to one another at portions thereof on the other end of the stator core. The stator can have regularly disposed coils more easily than the stator having a stator winding of continuously wound magnet wires.
In WO92/06527, there is no description about the insulator disposed between the conductor segment and the stator core. However, such electric insulators are necessary under some circumstances. It is preferable that such insulators are inserted into the slots easily together with the conductor segments. Such insulators are insulation layers known as insulation coatings of magnet wires, insulation sheets disposed between conductor segments and a stator core, or insulation layers covering inner surfaces of the slots of the stator.
It is well-known that a stator core is a lamination of stamped-out steel sheets having a plurality of slots. When the sheets are cut by a stamping machine, burs having sharp edges are formed on the peripheral corners of the sheet. The outer and inner peripheral edges of the stator core can be lathed or squeezed easily to remove the burs, thereby providing accurate sizes and roundness. However, the burs on the peripheral edges of the slots are not removed. Therefore, if conductor segments are merely inserted into such slots as disclosed in WO/92/62527, the insulation coating of the conductor segments may be broken by the sharp edges of the burs on the peripheral edges of the slots.
Therefore, a main object of the invention is to provide a stator of an ac generator that has a good insulation structure for protecting the slot-insulation layer from damage and a method of manufacturing its stator.
According to a main feature of the invention, a stator includes a stator core having a plurality of slots, a plurality of conductor segments disposed in the slots, and a plurality of insulation layers disposed between inner peripheries of the slots and the conductor members. The stator core is a lamination of steel sheets having the plurality of slots cut out in a cutout direction to provide burs projecting from each of the steel sheets in the cutout direction, and the conductor segments are inserted into the plurality of slots in the same direction as the cutout direction. Accordingly, the insulation layers are inserted into the slots smoothly and are not damaged when the conductor segments are inserted into the plurality of slots. Each of the conductor segments can have a U-turn portion at the back end of the stator core in the cutout direction.
The stator core is a lamination of steel sheets having the plurality of slots cut out in a cutout direction, and the electric conductors are inserted into the plurality of slots in the same direction as the cutout direction.
Accordingly, the conductor segments can be inserted smoothly into the slots.
Each of the electric conductor segments can have a U-turn portion at the back end of the stator core in the cutout direction. Therefore, the insulators can be prevented from being damaged when the conductor segments are inserted.
Each of the insulation layers can have a folded lip at the back end thereof in the cutout direction. As a result, the insulators can be prevented from being damaged when the conductor segments are inserted.
Each of the insulation layers can have a folded lip at the front end thereof in the cutout direction. As a result, the insulator can be prevented from being damaged when the conductor segments are bent to form coil ends.
Another object of the present invention is to provide a method of manufacturing such a stator.
According to another feature of the invention, a method of manufacturing a stator of a vehicle ac generator is composed of a first step of forming a lamination of steel sheets, a second step of cutting a plurality of slots from the lamination in a cutout direction, a third step of inserting insulators into the slots in the cutout direction, a fourth step of inserting conductor segments into the slots in the cutout direction; and a fifth step of connecting the conductor segments extending from the slots to one another.